The size and thickness of portable wireless communication apparatuses, such as mobile phones, have been rapidly reduced. In addition, the portable wireless communication apparatuses have been transformed from apparatuses to be used only as conventional telephones, to data terminals for transmitting and receiving electronic mails and for browsing web pages of WWW (World Wide Web), etc. Further, since the amount of information to be handled has increased from that of conventional audio and text information to that of pictures and videos, a further improvement in communication quality is required. In such circumstances, there are proposed a multiband antenna apparatus and a compact antenna apparatus, supporting a plurality of wireless communication schemes. Further, there is proposed an array antenna apparatus capable of reducing electromagnetic coupling among antenna apparatuses each corresponding to the above mentioned one, and thus, performing high-speed wireless communication.
According to an invention of Patent Literature 1, a two-frequency antenna is characterized by having: a feeder, an inner radiation element connected to the feeder, and an outer radiation element, all of which are printed on a first surface of a dielectric board; an inductor formed in a gap between the inner radiation element and the outer radiation element printed on the first surface of the dielectric board to connect the two radiation elements; a feeder, an inner radiation element connected to the feeder, and an outer radiation element, all of which are printed on a second surface of the dielectric board; and an inductor formed in a gap between the inner radiation element and the outer radiation element printed on the second surface of the dielectric board to connect the two radiation elements. The two-frequency antenna of Patent Literature 1 is operable in multiple bands by forming a parallel resonant circuit from the inductor provided between the radiation elements and a capacitance between the radiation elements.
According to an invention of Patent Literature 2, a multiband antenna includes an antenna element having a first radiation element and a second radiation element connected to respective opposite ends of an LC parallel resonance circuit, and is characterized in that the LC parallel resonant circuit is constituted of self-resonance of an inductor itself. The multiband antenna of Patent Literature 2 is operable in multiple bands due to the LC parallel resonant circuit constituted of the self-resonance of the inductor of a whip antenna itself.